KR19980063651A - Refrigeration system with single or multiple stage compressors with capacity control - Google Patents

Abstract

Compressors with multiple banks of cylinders can be operated in multiple stages, in one stage, in multiple parallel stages, and in multiple stages with or without an economizer. One of the lower banks of the cylinder may be unloaded to reduce the first stage output during multistage operation or to enable one stage operation when the second stage is bypassed.

Description

Refrigeration system with single or multiple stage compressors with capacity control

A refrigerated transportation facility may have a load requiring temperatures of -20 ° F for ice cream, 0 ° F for some frozen foods, and 40 ° F for flowers and fresh fruits and vegetables. have. The trailer will also have one or more compartments with loads having different temperature requirements. For some cargoes such as fruits, vegetables and flowers, thorough temperature control is required to avoid premature withering or blooming. In addition, the ambient temperature encountered will range from -20 ° F or less to 110 ° F or more. The wide range of load temperatures requirements, as well as the wide range of ambient temperatures that can be encountered on one-way trips, can widen the range of refrigeration capacity requirements. Multistage compressors are preferred for applications in refrigeration transport because they provide improved refrigeration capacity over conventional single stage compressors for a moderate cost premium. Currently available multi-stage compressor technology is difficult for the end user to use because it actually requires several external valves and pipes and has many application limitations needed for the compressor to operate reliably. Japanese Patent No. 53-133,257 discloses a multistage compressor arrangement. Commonly assigned U.S. Patent No. 5,577,390 relates to multistage compressor operation, and commonly assigned U.S. Patent Application 08 / 360,483 and current U.S. Patent 5,577,390 relates to capacity control in a multistage compressor. Commonly assigned US Pat. Nos. 4,938,029, 4,986,084, and 5,062,274 disclose reduced capacity operation in response to load requirements, while US Pat. No. 5,016,447 discloses a two stage compressor having an interstage refrigeration apparatus. have. In a reciprocating refrigeration compressor having multiple stages of compression, the intermediate pressure gas can be delivered through a crankcase barrel. However, using this approach for low temperature operation to significantly improve the efficiency, some cumbersome problems arise in medium and high temperature applications. The higher the crankcase pressure is generated, the lower the effective oil viscosity, the higher the thrust washer load and the higher the bearing load. Compressors with multiple cylinder banks can be operated in multiple stages during low temperature operation and can be operated in one stage or multiple parallel one stages in the case of medium and high temperature operation. In addition, economizer operation may be employed when the compressor is in two stages of operation. Switching between single and multistage operation is under the control of a microprocessor that responds to box temperature in the case of sensed suction or crankcase pressure or load pulldown. Multistage operation uses an economizer to provide increased capacity and lower pressure differentials between each stage. Reduced dose operation can be achieved by bypassing the first stage behind the suction, using a cutoff at the first stage, bypassing the entire stage, or bypassing the high stage.

Assuming a six cylinder compressor forms three banks of two cylinders, two outer or end banks are designated as low stage banks. One of the low stage banks LS-1 has a cylinder head shape which allows the economizer gas to be introduced into the discharge side of the cylinder head. The other low stage bank LS-2 is equipped with a standard anti-suction unloader head. The central bank of the compressor is designated as the high stage bank (HS) and has a cylinder head which allows exhaust gas from the low stage bank (LS-2) to cross over the suction side of the high stage bank (HS) inside the high stage bank (HS). Equipped. A valve plate for blocking the flow of suction gas from the crankcase to the suction side of the high stage bank HS is used.

The present invention simplifies its application and control of a multi-stage compressor by delivering suction gas directly into the crankcase and acquiring routing of intermediate gases. The only piping connection to the compressor can be a conventional suction and discharge connection and another connection for introducing the economizer gas. The only additional system components required in comparison to a normal one stage system may be an economizer, an economizer expansion valve, an economizer liquid line solenoid valve and a bypass tube valve.

Six stages of capacity control can be used in the compressor and system design of the present invention. The steps include the first stage loaded with two cylinders / one bank LS-1, the first stage loaded with both banks LS-1 and LS-2, and one low stage bank LS-1. Modified multistage operation with two cylinders, operation of the economizer and pumping to the high bank (HS) without such operation, and operation of the economizer and pumping into the high bank (HS) without such operation (LS-1, LS- 2) with conventional multistage operation.

It is an object of the present invention to provide a simplified multistage compressor design that allows intake gas to be delivered through the crankcase.

Another object of the present invention is to simplify the design and application of multistage compressors used in transport and stationary / commercial refrigeration systems.

It is a further object of the present invention to provide a compressor which can be operated in multiple stages or in one stage, wherein the single stage operation is a single stage operation or a plurality of parallel one stages. As will be seen later, these objects are achieved by the present invention.

Basically, the suction or crankcase barrel pressure and box or zone temperature are sensed and in response the compressor is operated in multistage or single stage mode. One-stage operation can be accomplished as multiple parallel banks or by unloading the first or second stages in a multistage operation. Economizer operation may be employed in multistage operation.

1 shows schematically a refrigeration system employing a compressor of the present invention;

2 is a schematic diagram showing a basic compressor;

Figure 3 shows a high side cylinder head.

4 is a sectional view taken along line 4-4 of FIG.

<Description of the code | symbol about the principal part of drawing>

12: compressor

14: crankcase

20: evaporator

22: condenser

30: economizer

40: pressure sensor

50: cylinder head

100: microprocessor

Microprocessor 100 performs overall control within refrigeration system 10 of FIG. The microprocessor 100 receives a zone input indicative of cooling requirements and, in response, starts or combines with the internal combustion engine driven compressor 12 (not shown) in the case of a refrigeration transport system and is a fixed / commercial refrigeration system. In the case of powering the motor-driven compressor (12).

The pressure sensor 40 senses the suction pressure in the crankcase 14, which is the main pressure indicator of the compressor 12 operation, and indicates the need to load the compressor 12 when the detected pressure is above a predetermined set point. In response to the pressure and zone inputs sensed by the pressure sensor 40, the microprocessor 100 controls the capacity of the compressor 12 and controls the system 10 by control of the solenoid valves SV-1 through SV-4. ). The solenoid valve SV-1 is normally open and the solenoid valves SV-2 to SV-4 are normally closed. Only one of the solenoid valves SV-2 to SV-4 can be open at any time. The solenoid valves SV-2 and SV-3 and the pipes on which they are disposed may be considered unnecessary or can be arbitrarily selected, usually only one is present in the system.

The piston (not shown) is reciprocally driven by a motor (not shown) via a crankshaft (not shown). The crankshaft is arranged in a crankcase 14 with an oil barrel disposed at its base. The compressor 12 has a suction tube 16 and a discharge tube 18 connected to the evaporator 20 and the condenser 22 of the refrigeration system 10, respectively. The economizer 30 and thermal expansion device (TXV) 32 are continuously disposed between the condenser 22 and the evaporator 20. The suction pipe 16 includes a crankcase 14 and includes a pipe 16-1 for supplying a cylinder of the first low stage bank LS-1, a suction prevention valve SV-1, and a second low stage bank ( It branches to the pipe 16-2 which supplies the cylinder of LS-2. When the intake prevention valve SV-1 is opened, the first and second banks LS-1 and LS-2 provide the medium pressure hot cooling gas as the intake plenum for the high stage bank HS. Discharge into the freenum (M). The high temperature high pressure gas discharged from the high stage bank HS is supplied to the condenser 22 through the discharge pipe 18 at the discharge pressure P _D. In the condenser 22, the hot cooling gas provides heat to the condenser air to cool the compressed gas and change the state of the coolant from the gas state to the liquid state. When the solenoid valve SV-4 is closed, the liquid coolant flows from the condenser 22 to the thermal expansion valve (TXV) 32 via the liquid conduit 24 and the non-operating economizer 30. As the liquid coolant passes through the orifice of the thermal expansion valve (TXV) 32, a portion of the liquid coolant will evaporate into a gas (flash gas). The mixture of liquid and gaseous coolant is passed through tube 26 to evaporator 20. The heat absorbed by the coolant from the air across the evaporator allows the liquid coolant to evaporate in a balanced manner within the coil of the evaporator 20. The evaporated coolant at evaporator pressure (P _EVAP ) is then fed to the lower banks LS-1 and LS-2 of the compressor 12, respectively, via the suction line 16 and the crankcase 14 to complete the fluid circuit. To the tubes 16-1 and 16-2.

By opening the solenoid valve SV-4, the microprocessor 100 converts a portion of the liquid coolant from the liquid tube 24 to the branch tube 24-1 and allows flow therethrough to allow the thermal expansion valve TXV to flow through. The economizer 30 is operated under the control of 34). When the solenoid valve (SV-4) and the thermal expansion valve (TXV) 34 as the servo valve are opened, the expanded coolant passes through the tube 24-1 at the economizer pressure P _ECON and passes through the bank LS-1. And a prenumer M representing the discharge prenum of the LS-2 and the suction prenum of the bank HS. Maximum capacity is obtained when solenoid valves SV-1 and SV-4 are open. By closing the solenoid valve SV-1, the unloading of the bank LS-2 by inhalation prevention reduces the total capacity by reducing a large amount of system flow, whether or not the economizer is operating.

When the solenoid valve (SV-4) is closed, the economizer will not operate and will have two stages of reduced capacity. In addition, the capacity reduction can be obtained by closing the solenoid valve SV-1, thereby unloading the bank LS-2 by the suction prevention. Reduced first stage by opening solenoid valve SV-2 to bypass the first stage for the bank HS to perform all pumping or by opening solenoid valve SV-3 to bypass the second stage. You can get it working. When the solenoid valve SV-3 is open, both banks LS-1 and LS-2 can be pumped or the bank LS-2 is closed by closing the solenoid valve SV-1. Can be unloaded. As mentioned above, the solenoid valves SV-2 and SV-3 can usually be arbitrarily selected.

When the solenoid valve SV-4 is opened and the solenoid valve SV-1 is closed, the operation of the economizer occurs and the bank LS-1 is pumped into the bank HS. The bank LS-2 is deactivated by the closing of the solenoid valve SV-1. In addition, the unloading of the bank LS-2 can be achieved by bypass of the hot gas. Closing the solenoid valve (SV-4) will cause the economizer to stop working.

When the solenoid valves SV-4 and SV-1 are closed and the solenoid valve SV-3 is open, one-stage operation takes place and the bank LS-1 can perform all the work. When the solenoid valve SV-1 is opened, parallel one-stage operation occurs and both banks LS-1 and LS-2 operate.

As mentioned above, the present invention requires a crystal cylinder head for a high stage bank (HS). Referring to FIG. 2 for the first time, the tube 16-1 is supplied to the suction chamber L of the bank LS-1 and the tube 16-2 is supplied to the suction chamber L of the bank LS-2. It can be seen that it is supplied. The chamber M in fluid communication with each other represents the discharge chamber of the banks LS-1 and LS-2 and the suction chamber of the bank HS. The chamber M of the bank LS-2 is in fluid communication with the chamber M of the bank HS through the passage H and the chamber H in the cylinder head 50 of the bank HS. Referring now to Figures 3 and 4, it can be seen that the partition 50-1 divides the cylinder head 50 into chamber M and chamber H. The valve plate (not shown) cooperates with the cylinder head 50 to form the chambers M and H of the bank HS. Inlets 50-2 and 50-3 are provided to accommodate bolt locations and provide a desired flow cross section. The inlets 50-2 and 50-3 engage the passage 50-4 and the corresponding part in the valve plate (not shown) of the bank HS is in fluid communication with the chamber M of the bank LS-2. do. Therefore, the fluid passage from the chamber M of the bank LS-2 to the chamber M of the bank HS includes the ports in the valve plate of the bank HS, the inlets 50-2, 50-3, And a passage 50-4 leading to the chamber M of the bank HS. As schematically shown in Fig. 2, the chamber M of the bank LS-1 is connected to the chamber M of the bank HS through a fluid passage, but it is connected to a special cylinder head (such as the passage 50-4). It does not require modification of 50).

Claims (6)

A closed circuit comprising a multistage compressor (12), a condenser (22), an economizer (30), and an expansion device (32) and an evaporator (20) in series, and a closed circuit intermediate said condenser and said economizer, said first Controlling the system in response to zones and system inputs, with branch pipes 24-1 having a flow path comprising a valve SV-4 and an expansion device 34 and the economizer and connected to the compressor in an intermittent position A refrigeration system (10) comprising a microprocessor (100) for The compressor comprises a first stage comprising at least two banks LS-1 and LS-2, a second stage, means for unloading one of the banks of the first stage SV-1, Means for unloading one of said first and second stages (SV-2, SV-3), The microprocessor controls the means for unloading one of the first valves and the banks and the means for unloading one of the first and second stages, such that the system is economical or economical. A refrigeration system, characterized in that it can be operated in first and second stages without in flow or with or without unloading one of the banks of the first stage. The refrigeration system of claim 1 wherein the means for unloading one of the first and second stages is to unload the first stage. 3. The refrigeration system of claim 2 wherein the means for unloading one of the first and second stages comprises a second valve. The refrigeration system of claim 1 wherein the means for unloading one of the first and second stages is to unload the second stage. The refrigeration system of claim 1 wherein the bank of the first stage comprises a discharge chamber, the second stage comprises a suction chamber, and the discharge chamber and the suction chamber are fluidly connected. 6. The method of claim 5, wherein the second stage has a discharge chamber, wherein the discharge chamber of the first stage and the suction chamber of the second stage pass through a flow passage extending through the discharge chamber of the second stage. Refrigeration system, characterized in that the fluid connection.